When you change the oil is the best time to do it. Take off the oil filter and there is a black box just above it. Plugged into the black box is the PCV valve with attached hose. You can pop it out carefully with a screwdriver. Then crawl out from underneath your car (safely supported with jackstands) and pull the hose that the PCV is attached to from between your intake runners and pop in the new valve. Crawl back under and put it in the black box. Finish oil change.

It took me and my friend about 20 minutes to find it on his EX. I couldn't believe they started putting those things underneath the intake manifold. They are hard enough to get out when there on top. Good thing he had small hands and could get the stupid thing out of the oil separator can though. I couldn't even get my hand in there far enough to get a thumb on it.